provided x is outside AV. We now treat AV as (macroscopically) infinitesimal, put it equal to dx', and integrate over all space to obtain the potential + P(x'). V' The second term is analogous to the dipole layer potential (1.25), but is for a volume distribution of dipoles. An integration by parts transforms the potential into (x) dx '[_P(x) 4 TEO X-X' (x) = 1/6 fdx. 4TEO [p(x')' P(x')] X This is just the customary expression for the potential caused by a charge distri- bution (pVP). With E= -VO, the first Maxwell equation therefore reads 1